What is selection pressure?

Selection pressure is an abstract force that shapes organisms as they evolve due to mutation, natural selection, and genetic drift. For instance, a selection pressure on the ancestors of giraffes for longer necks led to modern giraffes. Selection pressures on small mammals living in open plains led to muscular legs and adeptness at running. Selection pressure operates over durations as short as a few generations, and as long as millions of generations. Source: X



Yea, whatever. I only know wht is pressured by the word "selection"
SELECTION, efff youuuuuuu.

Class was alright tday, had some jokes, post them up next time.
Shall be a good girl, eat dinner and sleep.

Think tomorrow will be boring, because i have to stay back for a stupid trip!

Ipod or new phone?
but i feel tied down with a phone lehhhh!

oh, and haloscan, you suck! -.-